With the development of mobile communication technology, network coverage tends to be more complicated and diversified, such as the second Generation (2G) and the third Generation (3G) networks, in which UMTS Terristrial Access Network (UTRAN) is employed as Radio Access Technology (RAT), and Long Term Evolution (LTE) network, in which Evolved UMTS Terristrial Access Network (E-UTRAN) is employed as RAT. To ensure that users can enjoy conveniences of mobile communication technology at any time, a multi-mode mobile terminal which supports multiple networks has been developed. For a 2G/3G multi-mode mobile terminal, it can switch to the 2G network in the event that the 3G network experiences poor coverage, so that basic speech communication can be guaranteed. Alternatively, it can switch back to the 3G network in the event that the 3G network is in good coverage.
Typically, before conducting various services, a mobile terminal needs to search for an available network and registered with the network, for example, the network selection needs to be performed firstly when the mobile terminal is powered on, roaming, or lost in network coverage, so as to camp on the selected network. Currently, a list of Public Land Mobile Network (PLMN) sorted by priority may be stored in a Subscriber Identity Module (SIM) card, an Universal Subscriber Identity Module (USIM) card, or a Nonvolatile Memory (NVM) of a mobile terminal. Each item in the list may further contain a RAT type corresponding to a PLMN. In the event that a mobile terminal is powered on, roaming, or lost in network coverage, the mobile terminal may select a PLMN having the highest priority in the list; and, if the network selection fails, the mobile terminal may select a PLMN having the second highest priority in the list, until the network selection succeeds.
The conventional PLMN list only contains a PLMN and a RAT type corresponding to the PLMN. However, it fails to declare which duplex mode can be used by the PLMN. It is known that a duplex mode may be a Time Division Duplex (TDD) mode or a Frequency Division Duplex (FDD) mode. For example, Time Division-Synchronous Code Division Multiple Access (TD-SCDMA) or Time Division Duplexing Long Time Evolution (TDD-LTE) is a TDD mode, and WideBand Code Division Multiple Access (WCDMA) or Frequency Division Duplexing Long Time Evolution (FDD-LTE) is a FDD mode. For a multi-mode mobile terminal supporting both FDD and TDD, because a duplex mode is not specified in the conventional list, the mobile terminal may have to try both of the FDD and TDD modes so as to determine which duplex mode can be used to select the PLMN. In practice, for a given PLMN in a specified location, the PLMN supports only one duplex mode. Even if a network provided by a network operator supports both FDD and TDD, only one duplex mode is supported by the network on a certain network coverage spot. Therefore, for a mobile terminal supporting two duplex modes, problems may occur when network selection is performed according to the two duplex modes, such as the speed of network selection is lowered, and power consumption is increased. More information may refer to U.S. application No. US 20100015978A1, which discloses a method for selecting a preferred network for a multi-mode mobile terminal by using a PLMN list containing disparate groups of radio access technologies. However, this method fails to solve problems of quick network selection for a mobile terminal supporting multiple duplex modes.